The present invention generally relates to the correction of spinal deformities. Specifically, the present invention provides an improved apparatus and method for maintaining vertebrae in a desired spatial relationship.
Devices for correcting spinal column deformities are known. One such device is disclosed in U.S. Pat. No. 3,997,138 which has a pair of flexible rods or cables to maintain the position of adjacent vertebrae. The thin rods or cables are secured to fasteners connected with vertebrae.
Devices that include rigid plates are also known for the straightening of spinal deformities. The plates are relatively heavy and cannot be easily bent to have a curvature corresponding to the desired curvature of a particular spinal column. In addition, the rigid plates do not permit flexibility in locating the fasteners in the vertebrae.
Another known device for correcting spinal deformities includes a straight ratchet rod. The rigid ratchet rod applies compressive force to the spinal column when attached to vertebrae by hooks connected to the rod. This device does not conform to curves in the spine and only functions to compress the spine.
In another device, the corrective forces are generated by two steel rods which are wired around the spine. The rods may be bent to a desired curvature. The rods are not directly attached to all the vertebra that the rods span. Maintaining a desired spatial relationship between the vertebrae spanned by the rods is, at best, difficult.
Another known corrective device is disclosed in U.S. Pat. No. 4,041,939. The device includes a plurality of plates. Each of the plates is secured over one end of a vertebra. Fasteners are connected to the vertebrae through the plates. A cable is then crimped in the head of the fastener to attach the cable to one vertebra. Tension is put on the cable while it is crimped to an adjacent vertebra until the desired correction is accomplished. This device can only put compressive forces on the spine so that the cables are always in tension. Once the cable is crimped in place, no further adjustment between the crimped fastener and cable is possible.